Chapter 5
The Integumentary System
General Anatomy
• Skin and its
accessory
structures
• Objectives:
–
–
–
–
–
• A large organ
composed of all
4 tissue types
structure
function
growth and repair
development
aging
• Square feet?
• Thickness?
• Weight?
5-1
5-2
Overview
Functions of the Skin
epidermis
• Thermoregulation (sweat – blood vessels)
• Protection as physical barrier (cells junctions,
cancer prevent, dehydration)
• Sensory receptors (sensation)
• Excretion and absorption
• Synthesis of vitamin D (calcitrol)
• 2Types: thick & thin
• 2 Major layers of skin
(aka: cutaneous layer)
1) epidermis is epithelial
tissue
dermis
Sub-Q
2) dermis is all tissues
– AKA: Intradermal layer
• Subcutaneous layer
(aka: subQ or hypodermis)
(adipose & connective
tissue)
5-3
5-4
Cell types of the Epidermis
Overview of Epidermis
• Keratinocytes--90%
• Stratified
squamous
epithelium
• Blood vessels?
• 4 types of cells
• 5 distinct strata
(layers) of cells
– produce keratin
• Melanocytes-----8 %
– produce melanin pigment
• Langerhans cells
(Dendritic cells)
– From WBCs
– provide immunity
• Merkel cells
– deepest layer
– form touch receptor
5-5
5-6
1
Layers (Strata) of the Epidermis
Stratum Basale
• Stratum corneum
• Stratum lucidum
• Stratum
granulosum
• Stratum spinosum
• Stratum basale
• Deepest layer- single row of
cells
(AKA: stratum germinativum)
• Combination of merkel cells,
melanocytes, keratinocytes stem cells that divide
repeatedly
• Attached to basement
membrane
• Scattered protein forms keratin
higher up (tonofilaments)
5-7
5-8
Stratum Granulosum
Stratum Spinosum
• 8 to 10 cell layers
• Keratinocytes
• Melanin taken in by
phagocytosis
• Slides look spiny
• 3 - 5 layers of flat dying
cells (apoptosis!)
• keratohyalin granules:
(converts protein to
keratin)
• Lamellar granules:
release lipids that repels
water
5-9
5-10
Stratum Corneum
Stratum Lucidum
• Only in thick skin:
palms, fingers, & soles
• 3 - 5 layers of clear, flat,
dead cells
• Dead keratinocytes w/
lots of keratin
5-11
• 25 to 30 layers of flat
dead cells – lots of
keratin and
surrounded by lipids
• Continuously shed
5-12
2
Keratinization & Epidermal Growth
• Stem cells (stratem basale) produce
keratinocytes and other cells
• Cells are pushed towards surface (mitosis),
filling with keratin (keratinization)
• ~ 4 week journey
Dermis: 2nd layer of skin
• Connective tissue layer
composed of collagen &
elasticextra-cellular
fibers, fibroblasts,
Secretes
matrix
macrophages & fat cells
• Hair follicles, glands,
nerves & blood vessels
• 2 major regions of dermis
1 - papillary region
2 - reticular region
5-13
Papillary Region
5-14
Reticular Region
• Top 20% of dermis
• Composed of CT (w/ elastic fibers)
– Areolar tissue
• Finger like projections called dermal papillae
– Epidermial ridges downward
Functions:
– anchor epidermis to dermis
– contains capillaries
– contains Meissner’s corpuscles (touch) &
free nerve endings (pain and temperature)
• Connective tissue
(collagen and elastic fibers)
- strength, stretch, & return to shape
- Packed with oil glands, sweat gland ducts,
fat cells, hair follicles, blood vessels, nerves
Hypodermis – subcutaneous fat!
5-15
5-16
Skin Color
• melanin – most
significant factor in skin
color
– produced by
melanocytes
– accumulate in the
keratinocytes
• eumelanin – brownish
black
• pheomelanin - a reddish
yellow sulfur-containing
pigment
Lines of cleavage: direction of collagen fibers in reticular
region
5-17
Cellular
extension
of melanocyte
Epidermis
Pigment
granules
Golgi
apparatus
Melanocyte
nucleus
Basement
membrane
• Hemoglobin
• Carotene (pigment)
Dermis
6-18
3
Abnormal Skin Colors
Accessory Structures of Skin
• cyanosis – blueish hue - from O2 deficiency
• erythema – abnormal redness: dilated cutaneous vessels
• pallor – pale or ashen color: little blood flow so collagen shows through
– emotional stress, low blood pressure, circulatory shock, cold, anemia
• albinism – genetic lack of melanin that results in white hair, pale skin, and
pink eyes
– have inherited recessive, nonfunctional tyrosinase allele
• jaundice - yellowing of skin and sclera due to excess bilirubin in blood
– cancer, hepatitis, cirrhosis, other compromised liver function
• hematoma – (bruise) mass of clotted blood showing through skin
– hair
– oil glands
– sweat glands
– nails
6-19
Structure of Hair
Functions of Hair?
•
•
•
•
5-20
• Dead keratinized cells
• Shaft -- visible
Prevents heat loss
UV Protection
Protect eyes
Touch receptors
– medulla, cortex & cuticle
•
•
•
•
5-21
Root = below the surface
Follicle surrounds root
Blood vessels
Germinal cell layer
5-22
Medulla
Arrector pili
muscle
Cortex (tightly
packed cells)
Cuticle (scales)
Follicle surrounds the root
Sebaceous gland
papilla
Bulb
5-23
5-24
4
Hair Related Structures
The Hair Cycle.
• Arrector pili
– smooth muscle in
dermis
– Hair root plexus
– (nerves detect hair
movement)
Old club hair
Epidermis
Sebaceous
gland
Piloerector
New hair
Club hair
(detached
from matrix)
Club
Bulge
Hair matrix
Hair bulb
Degeneration
of lower follicle
Dermal papilla
Dermis
1 Anagen (early)
Anagen (mature)
(Growing phase, 6–8 years)
Stem cells multiply and follicle grows deeper into dermis; hair matrix
cells multiply and keratinize, causing hair to grow upward; old club
hair may persist temporarily alongside newly growing hair.
2 Catagen
(Degenerative phase, 2–3 weeks)
Hair growth ceases; hair bulb
keratinizes and forms club hair;
lower follicle degenerates.
3 Telogen
(Resting phase, 1–3 months)
Dermal papilla has ascended
to level of bulge; club hair falls
out, usually in telogen or
next anagen.
5-25
Glands of the Skin
• Specialized exocrine glands
found in dermis
•
•
•
•
Sebaceous gland (oil)
Sebaceous (oil) glands
Sudiferous (sweat) glands
Ceruminous (wax) glands
Mammary (milk) glands
Merocrine (Eccrine) sweat gland
Sudiferous
Sudiferous
5-27
Apocrinesweat
sweatgland
gland
Apocrine
Histology of skin glands
5-28
Sudoriferous (sweat) glands (2 types)
Sebaceous (oil) glands
1. Eccrine (sweat) glands
– most areas of skin
– secretory portion in dermis with duct to
surface
– perspiration/evaporation
2. Apocrine (sweat) glands
– axillary and pubic regions
– secretory portion in dermis with duct to
hair follicle
• Secretory portion in the dermis
• Most open onto hair shafts
• Sebum (oily substance)
– keeps hair and skin soft & pliable
– inhibits growth of bacteria/fungi
5-29
5-30
5
Fingernail Structure
Ceruminous glands
Free edge
Nail body
Nail groove
• Modified sweat glands produce waxy
secretion in ear canal
• Cerumin (earwax = oil and wax glands)
• ??? Function
Nail fold
Lunule
Eponychium
(cuticle)
Nail
root
Nail plate
Free
edge
5-31
Nail
body
Nail bed
Degrees of Burn Injuries
Nail fold
Eponychium
(cuticle)
6-32
Nail matrix
Degrees of Burn Injuries
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Partial-thickness burns
(a) First degree
Partial-thickness burns
Full-thickness burns
(b) Second degree
(c) Third degree
(a) First degree
(b) Second degree
Full-thickness burns
(c) Third degree
a: © SPL/Custom Medical Stock Photo, Inc.; b-c: © John Radcliffe/Photo Researchers, Inc.
Figure 6.13
6-33
Figure 6.13
6